Many medical procedures are performed using minimally invasive surgical techniques, wherein one or more slender implements are inserted through one or more small incisions into a patient's body. With respect to ablation, the surgical implement can include a rigid or flexible structure having an ablation device at or near its distal end that is placed adjacent to the tissue to be ablated. Radio frequency energy, microwave energy, laser energy, extreme heat, and extreme cold can be provided by the ablation device to electrically inactivate the tissue.
With respect to cardiac procedures, a cardiac arrhythmia such as atrial fibrillation or a focal atrial tachycardia can be treated through-selective ablation of cardiac tissue to eliminate or isolate the source of the arrhythmia. A popular minimally invasive procedure, radio frequency (RF) catheter ablation, frequently includes a preliminary step of electrocardiographic mapping followed by the creation of one or more ablated regions (lesions) in the cardiac tissue using, RF energy. In the case of atrial fibrillation ablation, multiple lesions are required to obtain a successful result. Often five, and sometimes as many as sixty, lesions may be required before a successful result is attained.
Deficiencies of radio frequency ablation devices and techniques have been overcome by using cold to do zero degree or ice mapping (at −20° C. for example) prior to creating lesions, as taught in U.S. Pat. Nos. 5,423,807; 5,281,213; and 5,281,215. However, even though combined cryogenic mapping and ablation devices permit greater certainty and less tissue damage than RF devices and techniques both the cryogenic and the RF devices are configured for spot or roughly circular tissue ablation.
Spot tissue ablation is acceptable for certain procedures. However, other procedures can be more therapeutically effective if multiple spot lesions along a predetermined line, or a single elongate or linear lesion is created in a single ablative step. Radio frequency ablation devices are known to be able to create linear lesions by dragging the ablation tip along a line while it is active.
WO 00/32126, WO 98/37822 and EP 1,129,670 each disclose catheters suitable for linear ablation. However, these catheters present practical difficulties to the surgeon in use. More specifically, the inner wall chambers of the heart, such as the atrial wall, are irregular and slippery and the surgeon encounters a problem in stably positioning the linear catheter in the desired location with sufficient contact at the catheter/tissue surface for the required amount of time to create an effective unbroken line of ablation.
A catheter designed to be more suitable for ablation of an irregular surface is disclosed in WO 99/52455. However, this catheter still suffers the problem that it is difficult to position it stabily and accurately due to the deformable nature of the tissue walls.
U.S. Pat. No. 6,595,989, US 2003/0204187 and US 2004/0034347 all suggest using an inflatable balloon to anchor a structure in a cardiac vessel orifice, such as the pulmonary vein. Such devices have the drawback that the structure can be anchored only in a select few positions where veins exist. It can be very difficult for the surgeon to create selective ablations at positions far away from the anchoring point in the vein, for example.
It would be beneficial if there existed apparatus that made it possible to push a linear ablating device against tissue walls (e.g. the wall of the heart muscle) so as to ensure good contact at all points along the whole active length of the linear ablating device without the device slipping out of position. It would also be desirable if there existed apparatus that gave the surgeon a high degree of freedom in positioning the linear ablating device such that a selected ablation can be performed easily and quickly at any point on the tissue that the surgeon chooses.